1. Field of the Invention
This invention relates generally to computer systems and more particularly to a system and method for communicating between hardware and software in a multiprogramming/multiprocessing environment.
Multiprogramming/multiprocessing computer systems require the use of a communications area in main storage for communications between hardware and software. (See the application entitled "System Base" invented by Calude Carre, filed on Dec. 2, 1974, having Ser. No. 528,951 and assigned to the instant assignee, now abandoned, and which application has been incorporated by reference herein). The system base is generally located at a fixed location in main memory, although this location may be changed or relocated through the use of a device such as a boundary address register (BAR). (See application entitled Arrangement for Initializing a Data Processing System, invented by William Woods, filed on Dec. 2, 1974, having Ser. No. 528,814 and assigned to the instant assignee, now abandoned, and further incorporated by reference in the instant application).
High performance computing systems find it necessary to store portions of the system base in internal scratchpad registers instead of main memory, and hence inaccessible and invisible to software running in the system. Accordingly, a problem results when software (i.e. the programmer) wants to change positions or change information of the system base which happens to be located in these internal central processor scratch-pad registers which software cannot access.
2. Prior Art
The problem has been solved in one of two ways. The first method is to simply re-initialize the entire system, loading the system base with different contents as a result of a new initialization process. This technique is extremely time-consuming and quite undesirable.
A second technique for solving the problem is to have the software employ special model-dependent properties of the particular machine on which it was running, to change the system base. This results in the very undesirable property of completely model-dependent software--a feature which certainly does not serve to endear a computer manufacturer to a customer.
What is needed therefore is a technique of changing information in the system base both in main memory and internal scratchpad registers making the system base in scratch-pad memory accessible to software but not visible to software i.e. cannot be read by the software.